Abstract
A sample of 100 lower secondary school pupils was carefully selected from those in whom all the upper and lower teeth had erupted with the exception of third molars by excluding those pupils who were defective in normal arch, suffered from the caries greater than C3 or those who did not show any symptom of the gingivitis at all. PMA indices obtained of these subjects were put to the computation of correlative coefficients (r) to find out what tooth or teeth would be most representative of PMA findings of the anteriors, molars and jaws.
As the result, it was found that the correlation between 16 teeth consisting of the upper and lower first molars and 12 anteriors, and jaws gave r=0.96, the coefficient being satisfactorily representative of the jaws. We call this the AM method of PMA indices.
The correlative coefficient between 12 upper and lower anterior and jaw PMA indices was r=0.74 with 1% less risk than the above AM method. Further, the correlative coefficient between upper and lower 12 anteriors and either 1||1, 21||12, 31||13 or 32||23 and between them and six teeth in 321||123 was respectively 0.76, 0.88, 0.80, 0.82 and 0.89.
The correlative coefficient between PMA findings of the upper and lower first molars to which 1||1, 21||12 or 321||123 was added and those of jaws was respectively 0.82, 0.84 and 0.85.
From these measurements, it is to be concluded that for epidemiological purposes, PMA findings of the upper and lower first molars to which those of the anteriors are added may be reasonably taken as representative of the jaws. For the purpose of school dental examination for pupils, on the other hand, those of the upper and lower first molars to which either 1||1 or 21||12 is added may serve as a reliable guide.
